The dynamics of the actin network at the leading edge of a cell are used to produce the mechanical forces necessary for cell migration. Because the cell membrane is the site where many of the proteins implicated in the regulation of retrograde flow are localized it is of particular interest to focus on retrograde flow solely at the cell membrane. All of the current knowledge about the dynamics of retrograde flow is known from observations of retrograde flow occurring in the cytoplasm, leaving unexplored any of the dynamic interactions between the actin network and the cell membrane. This proposal seeks to use total internal reflection fluorescence (TIRF) microscopy and transmission electron microscopy (TEM), combined with RNA interference, in Drosophila S2 cells to investigate retrograde flow, specifically at the cell membrane.